1. Field of the Invention
The present invention relates to an LED device having a humidity sensor. Particularly, it relates to an LED device having a humidity sensor that can monitor the internal condition in the LED portion and is possible to detect both the temperature and humidity simultaneously.
2. Description of the Prior Art
The conventional light emitting diode (LED) includes a LED chip adhered on a metal plate (usually is made by copper that has better heat dissipation characteristics). The adhering method is to add a silicon resin (mixed with silver powder) or ceramic material as a bonding layer between the LED chip and the metal plate. So, the bonding layer has a good electrical conductivity and a great thermal conductivity. When the ceramic material is used, addition metal leads (or connecting lines) must be added. After the LED chip is adhered on the metal plate, a transparent lens made by silicon resin can be formed to cover this LED chip.
However, during the manufacturing procedure of the above-mentioned conventional LED, it is difficult to detect or monitor the following items:
[1] the adhering condition between the LED chip and the metal plate;
[2] the durable times about temperature fluctuating cycles (repeating high temperature and low temperature);
[3] the heat resistance and aging effect of the silicon resin mixed with silver powder;
[4] the adhering condition about the silicon resin during a fabricating process;
[5] the separating condition (such as a crack or a gap) after using a period of time (when such separating condition occurs, small bubbles might generate so that the light quality is lowered, and the product life becomes shorter due to the oxygenized metal lines.
The LED aging or malfunction are caused by the following reasons.
[1] The LED chip is out of order. As shown in FIG. 1, when the silicon resin (mixed with silver powder) 912 is over-heated or aging, the LED chip 913 will gradually separate from the metal plate 911. Hence, its electric conductivity and thermal conductivity reduce. Consequently, heat 80 cannot be expelled from the LED chip 913.
[2] The high humidity influences its function significantly. Because of the cracks or separation, external air can go inside. About the cracks, they are generated in the silicon resin portion 914. As exhibited in FIG. 2, the silicon resin portion 914 generates many cracks inside, so that external air can go inside to contact with the LED chip 913. Obviously, the internal humidity increases. Furthermore, about the separation (as illustrated in FIG. 3), a gap S2 occurs between the silicon resin portion 914 and the metal plate 911, so that excess heat cannot be expelled from the LED chip 913. Hence, external air might go into these cracks or the gap S2. Not only it will generate some bubbles, but also it will influence the internal humidity condition in this LED. The cracks or gap S2 will decrease the light emitting quality and functions of this LED significantly.
Therefore, after the packing procedure of this LED, unless a destructive detecting method is taken, the internal condition of this LED cannot be known. However, such destructive detecting method cannot be used during a standard testing procedure for product quality. So, it is hard to find any potential defects of the product during the manufacturing or packing procedures.
It would therefore be desirable to invent or to develop a new product to overcome the above-mentioned problems.